The specific goals of this research are to evaluate the effectiveness of triorganotin compounds as potential insecticides against larvae and adults of vector mosquitoes and to develop structure-activity relationship(s) between a parameter or parameters of the molecule and their toxicity. Two species of mosquitoes will be used in the study. One species is Anopheles stephensi which is a vector of human malaria parasites. The second species to be studied is Aedes aegypti, the primary vector of dengue and fellow fever. The development of a new class of effective insecticide would be of tremendous value in the effort to reduce the spread of these highly debilitating and sometimes deadly diseases. Triorganotin compounds could potentially overcome problems with resistance to other insecticides. To accomplish these goals, triorganotin compounds will be tested for their effectiveness against mosquito larvae and on the adult female mosquitoes. Larvicidal studies will involve placing mosquito larvae and various concentrations of triorganotins together for 24 hours and determining the toxic effects of the compounds. A bottle-based bioassay method will be used to determine the toxicity of the triorganotins of the adult mosquitoes. The duration of insecticidal activity against adult mosquitoes on representative housing construction materials will also be evaluated. Finally, residue studies will be done to determine the long term effects of the compounds. After evaluating the results of these studies, new triorganotin compounds will be designed and synthesized with the aim of developing more effective compounds. To reduce the number of compounds that must be synthesized and tested, structure-activity relationships (QSARS) between a physical parameter or parameters of the triorganotins and their toxicity will be developed.